1981 -1990 and 1991 -2000 showed strong decline during the second decade with an average reduction of 5% per two decades. Despite the drastic decrease in S, the all India averaged surface maximum and minimum air temperatures have been increasing. But, the change in increase in maximum temperature from the first decade to second decade is only marginal under the present situation of drastic increase in greenhouse gas emissions, while the increase in minimum temperature has been doubled.

[1] In contrast to most of the world where solar dimming has changed over to solar brightening since late eighties, dimming continues unabated over the Indian region. This study investigates new insight into the origin of dimming over India. As the insolation at the surface is controlled by aerosols and clouds, we tried to separate out the two controlling factors by examining clear and cloudy sky days. From 1981From -2006, the rate of dimming is found to be twice as large during cloudy conditions (∼12 W/m 2 /decade) compared to that during clear sky conditions (∼6 W/m 2 /decade). The clear sky dimming is attributed to increasing aerosols. While the rate of dimming by clouds is similar during summer and winter monsoon seasons, the increased contribution to dimming by clouds during summer seems to come from increasingly deeper clouds covering increasingly larger area. During winter, dimming in cloudy conditions appears to be due to indirect effect of aerosols.Citation: Padma Kumari, B., and B. N. Goswami (2010), Seminal role of clouds on solar dimming over the Indian monsoon region, Geophys. Res. Lett., 37, L06703,

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[1] Scale interactions associated with small scale (<100 km) dynamics might play a crucial role in the distribution of aerosol in the Himalayan foothills region. Turbulence measurements from a horizontal flight path during Cloud Aerosol Interaction and Precipitation Enhancement EXperiment (CAIPEEX) are used to illustrate the scale interactions in the vertically sheared flow below the high-level subtropical westerly jet, which is important in the transport of pollution. Data analysis reveals the three dimensional property of large eddies that scale 10-12 km near the slopes, which could bring pollution from the valley to the Tibetan Plateau through a circulation adhering to the slopes. This circulation has a subsidence region away from the slopes and may also contribute to the buildup of pollution in elevated layers over the Plains. The vertical velocity and temperature spectra from research flight data showed clear indications of (À5/3) slope in the mesoscale range. The isotropic behavior of the velocity spectra was noticed for cloud-free traverses, while this behavior is distorted for cloudy conditions with the enhancement of energy at smaller scales as well as with low frequency gravity wave generation. A high-resolution cloud allowing model simulation over the flight path is used to examine the representation of these dynamical interactions in the numerical model. Based on the analysis of observational data and model inferences, a conceptual understanding of the flow in the region close to the foot hills and its role in the distribution of aerosol and cloud condensation nuclei is presented.Citation: Prabha, T.

Twilight photometric technique has been used in order to demonstrate that the middle atmosphere can be perturbed by the presence of tiny particles delivered after an encounter with cometary dust trails like the one produced by 55P/Tempel‐Tuttle. The presence of meteoric dust in the atmosphere from the Leonid activity that occurred from 2001 to 2003 was detected by the twilight photometer operated at Pune (18.5°N, 73.9°E), India. The November 2001 and 2002 Leonid storms, and the 2003 November outburst, caused significant enhancements of dust from just above the mesopause to the lower stratosphere. The present study shows the formation of meteoric dust layers at mesospheric levels and their subsequent descent to lower altitudes. The enhanced stratospheric layers are observed 4 to 8 days after the peak meteor activity.